In making siding, fencing, deck boards, and other extruded articles, manufacturers sometimes desire a multicolored final product, referred to as an accented, variegated, or streaked color. In some instances, the multicolored effect is accomplished by using a thin, coextruded layer, called a capstock, over a plastic substrate.
Using state of the art resins, when different colored pellets of the same base formulation are mixed together and then extruded, the colors mix in the extruder when the pellets melt to give a uniform colored article out of the extruder die.
Current methods for obtaining the multicolored effect, and to avoid the color melding, is to use a base resin with one softening point mixed with colored pellets of a higher softening point resin. During extrusion the base resin melts first and the zones of the extruder are adjusted in temperature such that the higher softening point resin melts toward the end of the extruder near the die and never completely melts into the base resin. The higher temperature softening point resin, e.g. polycarbonate (PC) and α-methyl styrene, however, generally does not have weathering properties as good as the base resin such that the streaked accent colors fade and chalk faster than the base color.
It would be desirable to have a formulation which does not result in such color melding upon extrusion.